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<h1>Helium, He</h1>

Helium (He) is a noble gas that is colorless, odorless, and tasteless. In the realm of optics, helium is frequently employed as a buffer gas in gas lasers such as helium-neon (He-Ne) and carbon dioxide (CO<sub>2</sub>) lasers. In He-Ne lasers, helium helps to excite neon atoms, thereby facilitating the laser action, while in CO<sub>2</sub> lasers, it assists in the quick dissipation of heat. Additionally, helium's low refractive index, which is close to that of a vacuum, makes it useful in interferometry and other precision measurement techniques. Outside of optics, helium is commonly used in cryogenic environments to achieve extremely low temperatures, which are essential for certain high-precision devices like superconducting magnets used in Magnetic Resonance Imaging (MRI). Despite being one of the most abundant elements in the universe, its applications are quite diverse.

<h2>External links</h2>
<ul>
<li><a href="https://en.wikipedia.org/wiki/Helium">Helium - Wikipedia</a></li>
<li><a href="https://www.webelements.com/helium/">Helium - WebElements</a></li>
<li><a href="https://webbook.nist.gov/cgi/cbook.cgi?ID=C7440597">Helium - NIST Chemistry WebBook</a></li>
</ul>
